1. Field of the Invention
The present invention is concerned with a measuring arrangement for a winding arrangement, suitably for a textile machine, to determine the process variables relates to the length of material, such as thread, let-off or taken-up; by means of a signal generator provided to a rotatable winding carrier.
2. Discussion of the Relevant Art
In a measuring arrangement of this type (German published application DE-OS No. 2,351,431), a roller is provided to the outer circumference of a thread winding on a partial warp beam. This roller is caused to rotate by frictional action and therefore is turned in accordance with the speed of thread let-off. The rate of rotation of the roller is converted into pulses which correspond to a predetermined thread length. These pulses are provided to a control arrangement which drives the motor of the partial warp beam in dependence upon the rotation of the main shaft of the principal warp knitting machine and a setting amount, so that for each rotation of the main shaft a predetermined length of thread is let-off from the warp beam.
When utilizing a length-measuring arrangement such as a roller, it has been found that errors of the order of 3% must be taken into account. This occurs, among other reasons, because: a. a certain amount of slippage is unavoidable, b. the roller, under influence of its own mass and depending upon the hardness of the warped thread, pushes itself into the winding to a greater or lesser extent, and c. the extent of mutual contact between the roller and the winding changes, depending upon the actual diameter of the winding.
Thus there is a need for a measuring arrangement of the hereinbefore described type which provides with greater precision, this process variable that depends upon the length of the taken-up or let-off material such as thread.